Although various designs of silk screen printers are known to the art, those machines are constructed for the application onto print material of one, and solely one, specific second pattern corresponding to a first pattern formed on the stencil.
The number of multi-colour silk screen printers proposed in the art is very limited, by which is meant a single printer in which a plurality of patterns are mutually applied to one and the same print material in superimposed orientation.
The present invention relates nevertheless to such a silk screen printer which is intended to produce multi-colour prints.
The European Patent Application No. 8711 1078.2 and the U.S. Pat. No. 4,589,335 describe and illustrate a silk screen printer which incorporates a plurality of sequentially positioned printing stations provided with printing tables over which there is located a stencil frame having a stencil stretched therein, and which enable a multi-colour print to be applied to one and the same print material.
In relation to the measures taken in accordance with the present invention, it can also be mentioned that the U.S. Pat. No. 4,516,495 also teaches a method for positioning in one printing position a second pattern, deriving from a first pattern formed on a stencil, in relation to print material intended to receive the second pattern, and in which method said second patterns are formed by creating conditions whereby a coating or ink paste for application to the upper surface of said print material is allowed to pass through the perforations or open mesh in the stencil, or cloth, which forms the first pattern, e.g. with the aid of a squeegee used in a silk screen printer.
It is proposed that when applying this known method the two dimensional position of the second pattern in relation to a reference point, normally a part of the frame of the printer, is stored in a memory, and that when the material on which the second pattern is to be printed is moved into a printing location, the intended position of the material or a pattern which has previously been applied thereon, is evaluated together with any discrepancy which might occur should the second pattern be applied to the material with said material in said intended printed position.
It is also proposed that a stencil carrying the first pattern and/or a printing table and/or the actual material itself, is moved in dependence on the size and direction of any discrepancy established, so that in this printing location the second pattern will be printed on the material with the earlier established discrepancy fully or satisfactorily compensated for.
When practising this earlier known method one or more means which detect and establish the position of the material is/are moved in between stencil and material in a printing location, so as to enable the size and direction of a discrepancy to be evaluated, and the material on the pattern is moved in a manner to compensate for any evaluated discrepancy before printing is commenced.
The teachings of the U.S. Pat. No. 4,221,165 also belong to the state of the prior art in the present respect. This patent describes and illustrates a silk screen printer which has a plurality of gripping beams which in a first position, a feed position, grip the material on which print is to be applied and are then registered in a second position, a print position, in which said print is applied to the material. This enables the material to be moved through a precise transport path of definite length, from the material feed position to the printing position. This precise material transport path is obtained because each of the gripping beams can be registered mechanically in both of said positions, in relation to the printer chassis or a part thereof.
It is also proposed that in addition to a first registering means, which co-acts with a gripping beam for registering the material in the first position, there is also provided separate means which co-act with the material in a manner to register the material precisely in said first position, such that a positionally registered gripping beam collects a pre-registered print material and transports the material to the printing position through a precise material transport path.